(718c) Energy Storage with Molten Metal Oxide

Energy storage will play a critical role for electrical power generation as we move towards using renewable resources, since many renewable energy sources are intermittent in nature. Reversible fuel cells have been proposed as a possible way to store energy; however, energy losses associated with the conversion between H₂O and H₂ and the volumes required for storing H₂ are serious impediments to this technology. To solve these problems, we propose to use the electrochemical oxidation of Sb and reduction of Sb₂O₃ in a solid oxide fuel cell (SOFC) as a means of energy storage. Both Sb (m.p. 903K) and Sb₂O₃ (m.p. 929K) are molten at typical SOFC operating temperatures (e.g. 973K). Furthermore, initial data for Sb electrode overpotentials indicates that these losses are very low. Although the Nernst potential for Sb-Sb₂O₃ equilibrium is relatively low, this is inconsequential for the energy-storage application. Finally, the volume associated with 1MW-h of energy is only 45 liters, based on cell performance that has already been achieved. The main goals of work in this area are to understand how cell performance is affected by Sb-Sb₂O₃ conversion. Mixing the metal and oxide phases is found to be a critical factor in determining cell performance.